/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/mem/mem.h"
#include "tool/viz/lib/convolution.h"

/**
 * Creates padded array of array indices.
 *
 * This can be used to virtualize the memory of a matrix in one
 * dimension, to make it easy to avoid out-of-bounds access.
 *
 * @return value needs free(retval - leftpad)
 */
unsigned *convoindex(unsigned leftpad, unsigned n, unsigned rightpad) {
  unsigned i, j, *p;
  if ((p = malloc(sizeof(unsigned) * (leftpad + n + rightpad)))) {
    i = 0;
    for (j = 0; j < leftpad; ++j)
      p[i++] = 0;
    for (j = 0; j < n; ++j)
      p[i++] = j;
    for (j = 0; j < rightpad; ++j)
      p[i++] = n - 1;
  }
  return p;
}
